Suction cylinder for transmitting a torque

ABSTRACT

A DEVICE FOR DRIVING A WEB OR STRIP OF MATERIAL BY A ROTATABLE SHELL IN WHICH THE STRIP IS HELD WRAPPED AROUND THE ROTATING SHELL BY SUCTION APPLIED FROM WITHIN THE SHELL IN WHICH THE REGION OF CONTACT OF THE STRIP ON THE ROTATING SHELL COVERS MORE THAN THE LIMITED AREA OF THE WRAPPING REGION TO WHICH THE SUCTION PRESSURE IS APPLIED. THE POINT OF CONTACT OF THE STRIP WHERE IT RUNS ON TO AND OFF THE ROTATING MEMBER DOES NOT OVERLIE THE SUCTION MEANS WITHIN THE ROTATING MEMBER BUT OVERLIES A PORTION OF THE INTERIOR WHICH IS CONNECTED TO THE ATMOSPHERE. SEALS WHICH SEPARATE THE SUCTION REGION FROM THE ATMOSPHERIC REGION ARE SEPARATED SLIGHTLY FROM THE ANNULAR WALL OF THE ROTATING MEMBER.

United States Patent [1113587362 [72] Inventors Peter Herzhofi [56] ReterencesCited h i s w u UNlTED STATES PATENTS ans re 9 ooglleflmme In]; 0 gang 3,118,582 1/1964 Rapoza 226/95 schwekhe"mmwassmhemkusen 3,162,345 12/1964 Gallard m1. 226/95 Kurt Browatzki, Opladen; Joseph Friedsam, Langenield; Max Heidenrelch, Leverkusen. all of Germany [21] Appl.No. 781,831

[22] Filed Dec. 6, 1968 [45] Patented" June 28, 1971 [73] Assignee AGFA-Gevaert Aktiengesellschaft Leverkusen, Germany [54] SUCTION CYLINDER FOR TRANSMITTING A Primary Examiner-Allen N. Knowles Attorney-Connolly and Hutz 7 ABSTRACT: A device for driving a web or strip of material by a rotatable shell in which the strip is held wrapped around the rotating shell by suction applied from within the shell in which the region of contact of the strip on the rotating shell covers more than the limited area of the wrapping region to which the suction pressure is applied. The point of contact of the strip where it runs on to and off the rotating member does not overlie the suction means within the rotating member but overlies a portion of the interior which is connected to the atmosphere. Seals which separate the suction region from the atmospheric region are separated slightly from the annular wall of the rotating member.

SUCTION CYLINDER FOR TRANSMITTING A TORQUE The invention relates to a suction cylinder for transmitting torque to a web or a strip, more especially to a web with a photographic coating. The shell of the suction cylinder is perforated and its inner volume which is under suction effect is provided with a sealing body outside the wrapping angle and in contact-free manner relative to the perforated shell.

Such suction cylinders are for example used for converting a torque into tractive force in connection with photographic paper webs in casting machines when the static friction between the transmitting cylinder and the web is insufficient.

In known suction cylinders the sealing segment arranged internally in the cylinder covers with a slight overlap that part of the cylinder around which the web is not wrapped and leakage air passes through the shell perforation into the gap between the shell and the sealing segment and causes an undesirable fluttering of the web at the places where the latter runs on to and off the cylinder. This fluttering impairs the uniform forward movement of the web. In order to keep the defects small, the subatmospheric pressure has so far been limited to a few hundred mm. water column, whereby however the torque which can be transmitted remained small.

It has now been found that this disadvantage can be obviated and a larger torque can be transmitted if, in the region of the line where the web or strip runs on to and off the cylinder, the sealing body is provided with a groove transversely of the direction of travel of the web. The sealing body can also be provided with an annular gap segment, which groove or grooves communicate with the atmosphere through a bore arranged in the shaft.

This particular construction avoids air being sucked in through the perforated shell and the sealing gap. According to the new construction, the leakage air is in fact sucked out of the grooves through the sealing gap, so that the web is not subjected to any hannful force effect.

According to one particular embodiment of the invention, an annular body provided with two chambers is arranged in the perforated cylinder, said body leaving an annular gap relatively to the suction cylinder. The gap is provided just before the ends of the wrapping region with sealing webs and divides the annular gap into two segments, that segment lying in the region of the wrapping angle being connected to the chamber which is under suction effect and the other segment communicating through the second chamber with the atmosphere. In this embodiment, therefore, the two grooves are combined into one annular gap segment. This construction is sturdy and particularly desirable for manufacturing reasons.

The essential feature of the invention is to be explained by reference to one constructional example shown diagrammatically in a drawing, wherein; A

FIG. 1 shows the suction cylinder in cross section, along the line AB of FIG. 2, and

FIG. 2 shows the suction cylinder in longitudinal section.

In FIG. 1, a rotatable cylinder 3 has a shell 1 is formed with openings 2, and the cylinder encloses an annular body 4, while leaving two annular segmental gaps 5 and 6, which are separated from one another by sealing webs 7. The annular segmental gap 5 is disposed in the region beneath the wrapping angle of a web 8 and is connected via opening 9 with a chamber 10, which in its turn communicates through opening 11 with that passage 12 of core 13 which is connected to a suction pump (not shown). In the region around which the web 8 is not wrapped, the annular segmental gap 6 is connected through opening 14 with chamber 15, from which the opening 16 leads into the second bore 17 (FIG. 2) of the core 13, which is open to the atmosphere.

In FIG. 2, the cylinder 3, the shell 1 of which is formed with holes 2, is rotatably arranged by means of bearings 18 on the core 13 of the annular body 4. Partition 19 separates the two bores 12 and 17 from one another.

We claim: 1. In a device for transmitting motion to a strip of material,

the combination of a rotatable cylindrical hollow drive member having an interior surface, a first passage and a second passage, each passage at the interior surface of said drive member and extending transversely across and circumferentially along said interior surface, a central core forming said passages, a pair of seals associated with said core and adjacent to but not contiguous with said movable interior surface arranged to separate said curved passages from each other, perforations extending radially through the cylindrical wall of the drive member and opening into one of said curved passages, so constructed and arranged that the circumferential region of the drive member which is contacted by said strip extends over the first passage and at last a part of the second passage immediately adjacent a seal, means connecting said first passage with a suction-producing means, and means connecting the second passage with the atmosphere whereby in the regions where the strip runs onto or off of the cylinder extends over a passage which transversely underlying the contact of the strip on the drive member is at atmospheric pressure.

2. In the device claimed in claim 1, two chambers in said core, said passages formed by said core being of annular shape, said pair of seals being positioned within the drive member immediately adjacent to but spaced within the ends of the wrapping region of said strip contacting the outer surface of the drive member, said seals dividing the first and second annular passages so that the first passage lies entirely within the region of the wrapping angle and is connected to one of the chambers which is under a suction effect while the second passage communicates with the atmosphere through the second of said chambers. 

